Drill bit grinding fixtures



Jan. 17, 1956 J. v. NOVAK 2,730,349

DRILL BIT GRINDING FIXTURES Filed Sept. 20, 1952 3 Sheets-Sheet lInventor JAMES M NpvAK Jan. 17, 1956 J. V. NOVAK DRILL BIT GRINDINGFIXTURES I5 Sheets-Sheet 2 Filed Sept. 20, 1952 Inventor JAMES V. NOVAKJ. V. NOVAK DRILL BIT GRINDING FIXTURES Jan. 17, 1956 3 Sheets-Sheet 3Filed Sept. 20, 1952 Inventor JAMES V. Novm han United States PatentDRILL BIT GRINDING FIXTURES James V. Novak, Ber-Wyn, Ill.

Application September 20, 1952, Serial No. 310,640

1 (Ilaim. (Cl. 51-219) This invention relates to drill bit grindingfixtures. It utilizes a novel and unique control linkage, producing highaccuracy and efiiciency at minimum cost.

It is a primary object to provide a fixture which allows either fiat orhollow grinding of a well-balanced tool face, with rapid or slow cuttingcharacteristics, as desired.

A further object is to compensate for gradual changes of grinding wheeldiameters.

Another object is to minimize irregular wear of grinding wheel surfaces.

Still other objects, and pertinent features and advantages of the newdevice, will be mentioned in or will appear from the detaileddescription of a simple embodiment, which follows. In this descriptionand in the drawing illustrating the same specific details are disclosed,for full explanation of the illustrative example. It should beunderstood that the invention can be embodied in modified forms, whichare likely to occur to persons skilled in the art upon a study of thedisclosure. The exact scope of the invention will be defined by theclaim appended hereto.

In the drawing:

Figure l is a perspective view of a simple embodiment, in operativeposition to grind the face of a drill bit.

Figure 2 is an enlarged side view of the drill bit and the mechanismdirectly connected therewith, in the new fixture. Certain parts areomitted while others are shown in section, in a plane indicated by lines2-2 in Figure 1.

Figure 3 is a partial view of the same device in a different operativeposition thereof. The view is taken in the same plane as mentioned withrespect to Figure 2.

Figure 4 is a plan view of the device.

Figure 5 is a motion diagram, indicating how the device, seen in a viewlike that of Figures 2 and 3, moves from the position of Figure 2through that of Figure 3 into a final position.

Figure 6 is a further motion diagram, indicating how the center of thetip of the drill bit, seen in an axial direction, moves over the surfaceof the grinding wheel, during the motion illustrated in Figure 5.

Figure 7 is a detail section, taken along lines 7-7 in Figure 2.

Figure 8 is another detail section, taken along lines 8-8 in Figure 2.

Figure 9 is a detail view taken along lines 9-9 in Figure 2; and

Figure 10 is a detail section, taken along lines 10-10 in Figure 2.

The device is mounted adjacent a grinding wheel 11, upon a suitablebracket or support 12 to which it may be secured by clamps 13 or thelike. A blunted, chipped or generally damaged drill bit 14 lies in anopen-top channel 15 of V-shaped cross-section, which is supported andguided by linkage generally shown at 16. This linkage forms an importantpart of the invention. It is in turn supported and guided by a frame 17,which also serves to steady the channel and the drill bit lying therein.For

2,730,849 Patented Jan. 17, 1956 ice the latter purpose the channel isprovided with elongated cheeks or flanges 18, depending from the upperedges of the trough 15 and having sliding fit with the upstanding wallsor checks 19 of the frame 17. The bottom 20 of the frame is adjustablysecured to a base plate 21 for the entire fixture, for instance by ascrew 22, nut 23 and spring washer 24.

As shown in Figure 4 the base plate 21 has a straight side adjacent thegrinding wheel, which is best oriented parallel with the grindingsurface. The frame 17 is secured to the base plate at an angularitymatching the angle of the bit to be ground. For standard drill bits thisis 33 /2 degrees, approximately as shown in Figure 4; and it isdesirable to cut off one side of the base plate at this standardangularity, as shown, thereby facilitating the re-establishing of thestandard angularity. The device can be installed in front of acylindrical wheel surface as shown, or alternately in front of a flatwheel surface, at similar angularities. The front end of the channel iscut off diagonally so that it is normally parallel with the grindingsurface.

The linkage 16 substantially consists in two straight links 25, 26,having slightly different length, for reasons to be explained shortly.Each link 25 and 26 has a lower end secured to the frame 17 atsubstantially the same elevation above the bottom 20, by pivot pins 27,28 respectively. At a higher elevation there are additional pivot pins29 and 3G, securing the upper ends of the links 25, 26 to the flanges 18of the channel 15, at a shorter distance from one another than isprovided between the lower pins 27, 28. The ends 31 of the upper pins29, are peened flush with the outside surfaces of the channel flanges18, in order to avoid interference with the frame walls 19, which guidethe channel.

The links 25 and 26 are preferably made as short as possible in order tominimize bending moments. In this connection it will be noted that bothlinks are made as channel members. The flanges 32 of these channelmembers are basically used to provide bearings for the pins 27, 28, 29and 30. Additionally, the two flanges of each link 25 or 26, reinforcedby the intermediate web 33, provide adequate strength against thestresses encountered in the operation of the fixture. The links can bemade particularly short by cutting off upper parts of each web in formof a V, as shown at 34 in Figures 8 and 9. In this manner the short,reinforced links 25, 26 and the bottom of the channel 15 are allowed toswing relative to one another and to collapse to an adequate degree, asnoticeable mainly from Figure 2. No loss of strength is incurred, theweb 33 of each link being cut off only between the flanges 32 and theentire link being suitably reenforced by the web and flanges at the twoside edges, where such reenforcement is required.

The drill bit 14 is held, against axial pressure applied thereto by thegrinding wheel, by a sleeve 35. This sleeve substantially surrounds thechannel 15. It can be secured thereto by a thumb screw 36, threaded intoa part of, or washer within, the sleeve 35, below the channel 15.Pressure is thus applied against the bottom of the channel 15. Thedevice can be adjusted to various lengths of drill bits by sliding thesleeve 35 along the channel 15. Further, a fine adjustment is provided.Each end of the sleeve 35 has an ear 37, depending into the channel 15;and a screw 38 is threaded in these cars, in a direction parallel withthe channel. The head 39 of this screw will properly abut against theshank end of the drill bit. The other end of the screw has an adjustmentknob 40 secured thereto.

Proper position of the drill bit is additionally enforced by a finger41, made of spring steel or the like. This finger is pivoted to the topof the sleeve 35 by a rivet 42. When properly oriented along the channel15 the finger 7 base plate 21, while the front edge of that plate is setparallel with the grinding surface. The drill bit 14 to be sharpened isthen placed in the channel 15, with its rough edge about one-eighth toone and one-half of an inch in front of the front edge of the channel.The required projection of the bit in front of the channel dependsmainly on the exact installation of the support bracket adjacent thegrinding wheel, and the exact amount of steel to be removed.

Next, the slide 35 is moved up to the shank of the bit, and fastened byturning the thumb screw 36. Finger 41 is then swung in place andfastened at 43. A final fine adjustment of the drill bit, toward thewheel, can be made by turning the knob 40 of the screw 38. 1f the drillbit has a pointed shank end, care must be taken to avoid lifting thisend from the channel. The slot in the head of'thescrew 38 may have to beplaced in vertical position at the end of the adjustment, or some otherobvious precaution may have to be taken, when drill bits of relativelylarge or relatively small size are handled, as compared with that sizewhich brings the point of the shank end to the exact center of thescrew.

In actual'operation, the user of the fixture will generally hold thefree end of the channel in his left hand, with his left thumb on thefinger 41 and his right thumb on the drill bit between the front andback ends. The starting position of the channel is that wherein the freeend is at a low point, due to the weight of the channel and drill bit.This is shown in Figure at 14A. The operator now lifts the free end ofthe channel, with his left hand, until it reaches the position 14-G. Asa result the linkage 16 causes the tip of the drill bit to movedownwards. In the side view of Figure 5 the projection of this movementappears as a curve gradually approaching the grinding surface; in theaxial view of Figure 6 it appears as a curve a to g sweepingtransversely over the grinding surface. The curve lies in the planedefined by the orientation of the frame walls 19, which guide thechannel 15. At 14A the drill bit is out of contact with the wheel if thesupport bracket 12 and baseplate 21 thereon are properly positioned.Contact is made adjacent B or C. Steel is then removed from the wornface of the bit, by the rotating grinding wheel. Between the approximatelimits C and D such removal takes place back of the cutting edge of thebit; adjacent D or E the edge itself is finished. This change isgradual. It is obtained by the turning of the bit, incident to thelifting from 14-A to 14-G.

This change tends to produce a face of somewhat convex form, like acylinder segment that is, a drill bit edge (in Figures 2 and 8, finger41 has 4 this subframe. slots 48 in the frame walls 19. The adjustmentscrew 47 is secured against displacement due to vibration, by acompression spring 49 surrounding the shank of this screw and pressingagainst tabs 51 51, on frames '17, 46 respectively, wherein the screw 47is held. Upon an adjustment at 47, the extension, location and exactshape of the curve a g is modified but the general character of themotion and action remains the same as described; the shape of the groundbit however being changed, minutely but significantly.

The linkage adjustment 45 can also be used to compensate for the gradualwearing off of a cylindrical grinding wheel surface Minor adjustments ofthe screw 47 are generally sulficient for this purpose. It will be notedthat such adjustments can be made very readily; no pr eparatoryloosening of nuts or more complex operations are required.

The wearing of the grinding wheel is not only compensated by this simpleadjustment; it is also reduced and balanced by the transverse sweep ofthe curve a g. irregular wearing and frequent need for truing arepracticsily eliminated in this manner.

As a result, excellentdrill bit faces can be produced, often with betterquality than originally provided by the drill bit manufacturer. This canbe achieved with great economy as to the grinding fixture, and furthereconomy as to the wearing off of the grinding wheel;

The manufacture of the new fixture is simple. Stainless steel sheetingof uniform gauge thickness can be used for all special parts 15, 17, 21,25, 26, 35 and 46. The material need not be machined; punching andbending is suthcient for practical purposes.

I. claim:

A drill bit grinding fixture comprising a channel; a pair of links ofdifferent lengths having their upper ends pivoted to the channel atpoints spaced from one another longitudinally of the channel, and a basepivoted to the lower ends of the links at points more widely spaced fromone another, longitudinally of the channel, than the first mentionedpoints are spaced; each link substantially consisting in a short channelmember the flanges of which are pivoted to the channel and base, and theweb of which channel member has a substantially V-shaped recess, thecross section of the channel being similarly substantially V-shaped.

References Cited in the file of this patent UNITED STATES PATENTS183,798 Champlin Oct. 31, 1876 368,356 Root Aug. 16, 1887 523,897 KenyonJuly 31, 1894 571,336 Budlong Nov. 17, 1896 589,398 Ruldolphi Aug. 31,1897 1,020,860 Vauclain Mar. 19, 1912 1,052,968 Rodgers Feb. 11, 19131,063,391 Rodgers June 3, 1913 2,074,733 Porter Mar. 23, 1937 2,152,729Char-tier Apr. 4, 1939 2,248,263 Wiiliams July 8, 1941 2,394,839 BowmanFeb. 12, 1946 FOREIGN PATENTS 4,554 Great Britain Apr. 13, 1885 199,268Great Britain June 21, 1923 It is held slidably by horizontal guide

